Estudo de efeitos ambientais que influem na forma da curva de lactação de cabras mestiças no estado da Paraíba
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Data
1999-08-01
Autores
Ribeiro, Maria Norma [UNESP]
Pimenta Filho, Edgard Cavalcanti
Título da Revista
ISSN da Revista
Título de Volume
Editor
Sociedade Brasileira de Zootecnia
Resumo
O objetivo deste experimento foi estudar a influência de efeitos ambientais sobre a forma da curva de lactação (produção no pico, tempo de pico e persistência) de cabras mestiças Alpina x Gurguéia, ajustada pela função gama incompleta. Dados de 6126 controles, referentes a 877 lactações de 366 cabras criadas na Fazenda Carnaúba, localizada no município de Taperoá, Estado da Paraíba, no período de 1988 a 1995, foram usados. A função foi ajustada por regressão linear, após transformação logarítmica, e pelo método iterativo não-linear. Os parâmetros obtidos por regressão linear tiveram coeficiente de determinação ajustado de 71% versus de 90% obtido para a regressão não-linear. Produção máxima, tempo de pico e produção no pico foram obtidos por intermédio da função ajustada por regressão não-linear, que apresentou ajuste superior. O estudo dos efeitos ambientais sobre estas características foi realizado pelo método dos quadrados mínimos, usando um modelo contendo os efeitos de tipo de parto, ordem de parto, ano do parto e estação de parto. Os efeitos ambientes influenciaram todas as características estudadas. Maiores picos de produção foram observados para as cabras adultas, o que foi justificado pelo completo desenvolvimento fisiológico dos animais.
The objective of this experiment was to study the effect of environmental factors on the shape of lactation curves (peak yield, time of peak and persistency) of crossbred Alpine x Gurguéia goats fitted by Incomplete gamma function. Data from 6126 records of 877 lactation of 366 goats raised on Carnaúba Farm, Taperoá city, Paraíba State in the period from 1988 to 1995 were used. The function was fitted by linear regression, after logarithmic transformation and by non-linear iterative method. Adjusted coefficient of determination for linear regression was 71% versus a of 90% obtained by non-linear regression. Peak yield, time of peak and persistency were obtained by fitting the non-linear regression, that showed superior fit. The study of environmental effects on those traits was made by least squares method, including in the model the following factors: calving type, calving order, calving year and calving season. The environmental effects affected all the studied traits. Higher milk peak yields were observed for adult goats, which was justified by the complete physiological development of these animals.
The objective of this experiment was to study the effect of environmental factors on the shape of lactation curves (peak yield, time of peak and persistency) of crossbred Alpine x Gurguéia goats fitted by Incomplete gamma function. Data from 6126 records of 877 lactation of 366 goats raised on Carnaúba Farm, Taperoá city, Paraíba State in the period from 1988 to 1995 were used. The function was fitted by linear regression, after logarithmic transformation and by non-linear iterative method. Adjusted coefficient of determination for linear regression was 71% versus a of 90% obtained by non-linear regression. Peak yield, time of peak and persistency were obtained by fitting the non-linear regression, that showed superior fit. The study of environmental effects on those traits was made by least squares method, including in the model the following factors: calving type, calving order, calving year and calving season. The environmental effects affected all the studied traits. Higher milk peak yields were observed for adult goats, which was justified by the complete physiological development of these animals.
Descrição
Palavras-chave
curva de lactação, cabras, função gama incompleta, lactation curve, goats, incomplete gamma function
Como citar
Revista Brasileira de Zootecnia. Sociedade Brasileira de Zootecnia, v. 28, n. 4, p. 868-874, 1999.